R. Wesson (1), D. Stock (1,2), P. Scicluna (1)
(1) Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom. (2) Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7, Canada.
Calculations of the chemical abundances in photoionised nebulae rely either on the construction of a realistic physical model and the comparison of the predicted spectrum with observed, or the application of a number of simplifying assumptions to derive the abundances from observed emission line ratios. In practice, the second method is far less time consuming and therefore more often used. However, the systematic and statistical uncertainties in this approach are often difficult to quantify.
We have developed a code to calculate the physical conditions and chemical abundances from observed emission line fluxes, from both collisionally excited lined and the much fainter recombination lines. Our code calculates meaningful uncertainties using a Monte Carlo technique. We use the code to assess the magnitudes of both statistical and systematic uncertainties.
Poster presented at IAU Symposium 283, Planetary Nebulae: an Eye to the Future, 25-29 July 2011, Tenerife, Spain.